/*
 * Copyright 2013-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.netflix.ribbon;

import java.util.Map;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.StringUtils;

/**
 * @author Dave Syer
 */
public class RibbonClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {

	/**
	 * 解析标记了{@link RibbonClients} 注解的配置类，并构建{@link RibbonClientSpecification}
	 *
	 * @param metadata annotation metadata of the importing class
	 * @param registry current bean definition registry
	 */
	@Override
	public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
		// 我们在使用@RibbonClients注解的时候，可以单独为微服务配置Ribbon的配置，如下所示
		//@RibbonClients(value = {
		//@RibbonClient(name = "mall‐order",configuration = RibbonConfig.class),
		//@RibbonClient(name = "mall‐account",configuration = RibbonConfig.class)
		//})
		// 还可以统一设置默认，如下所示：
		// @RibbonClients(defaultConfiguration = { RibbonConfig.class})
		// 下面这个注册BeanDefiniion将这些配置注册为RibbonClientSpecification类型的Bean
		Map<String, Object> attrs = metadata.getAnnotationAttributes(RibbonClients.class.getName(), true);
		if (attrs != null && attrs.containsKey("value")) {
			AnnotationAttributes[] clients = (AnnotationAttributes[]) attrs.get("value");
			for (AnnotationAttributes client : clients) {
				registerClientConfiguration(registry, getClientName(client), client.get("configuration"));
			}
		}
		// 默认配置
		if (attrs != null && attrs.containsKey("defaultConfiguration")) {
			String name;
			if (metadata.hasEnclosingClass()) {
				name = "default." + metadata.getEnclosingClassName();
			} else {
				name = "default." + metadata.getClassName();
			}
			registerClientConfiguration(registry, name, attrs.get("defaultConfiguration"));
		}
		Map<String, Object> client = metadata.getAnnotationAttributes(RibbonClient.class.getName(), true);
		String name = getClientName(client);
		if (name != null) {
			registerClientConfiguration(registry, name, client.get("configuration"));
		}
	}

	private String getClientName(Map<String, Object> client) {
		if (client == null) {
			return null;
		}
		String value = (String) client.get("value");
		if (!StringUtils.hasText(value)) {
			value = (String) client.get("name");
		}
		if (StringUtils.hasText(value)) {
			return value;
		}
		throw new IllegalStateException("Either 'name' or 'value' must be provided in @RibbonClient");
	}

	/**
	 * 注入{@link RibbonClientSpecification}的BeanDefinition，搞半天RibbonAutoConfiguration里面的
	 * <p>
	 * //@Autowired(required = false) private List<RibbonClientSpecification> configurations = new ArrayList<>();由这里产生的。
	 *
	 * @param registry
	 * @param name
	 * @param configuration
	 */
	private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name, Object configuration) {
		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(RibbonClientSpecification.class);
		builder.addConstructorArgValue(name);
		builder.addConstructorArgValue(configuration);
		registry.registerBeanDefinition(name + ".RibbonClientSpecification", builder.getBeanDefinition());
	}

}
